The present disclosure relates to thermostats.
A thermostat may be used to control flow of coolant between a heated device and a heat exchanger to control the temperature of the heated device. The heated device may be, for example, an engine that heats up as it operates. The heat exchanger may be, for example, a radiator associated with the engine to cool liquid coolant that circulates through the engine for cooling the engine. The thermostat may be The thermostat may be used to direct coolant from the engine back to the engine so as to bypass the radiator to warm up the engine when the engine is cold. When the engine reaches a desired operating temperature, the thermostat may allow coolant to begin to flow to the radiator to prevent engine overheating.
The present invention comprises one or more of the following features or combinations thereof. A thermostat is provided for controlling flow of coolant between a heated device and a heat exchanger. The thermostat comprises a valve and an electric valve actuator to move the valve relative to a valve seat to control coolant flow.
According to one aspect of the invention, the electric valve actuator comprises an output member movable to a valve-seating position to position the valve against the valve seat. A wax motor of the thermostat is responsive to a predetermined temperature to move the valve away from the valve seat when the output member is positioned in the valve-seating position.
According to another aspect of the invention, the valve comprises a coolant passageway. The coolant passageway extends axially through the valve to facilitate axial movement of the valve in the coolant by the output member.
Other features of the thermostat may involve a housing. The housing comprises a coolant inlet and first and second coolant outlets. The coolant inlet is used to admit coolant from the heated device into the housing. The first coolant outlet is used to discharge coolant to the heat exchanger. The second coolant outlet is use to discharge coolant back to the engine to bypass the heat exchanger.
The electric valve actuator may comprise an electric motor, such as a stepper motor, to axially move the output member between a first valve-seating position and a second valve-seating position. In the first valve-seating position, the output member is positioned to position the valve against a first valve seat to block coolant flow between the coolant inlet and the first coolant outlet and apart from a second valve seat to allow coolant flow between the coolant inlet and the second coolant outlet. In the second valve-seating position, the output member is positioned to position the valve against the second valve seat to block coolant flow between the coolant inlet and the second coolant outlet and apart from the first valve seat to allow coolant flow between the coolant inlet and the first coolant outlet.
The wax motor may comprise a piston and a thermal expansion device with wax. The wax is responsive to the predetermined temperature to relatively axially move the piston and the thermal expansion device to axially move the valve away from the first valve seat to allow flow between the coolant inlet and the first coolant outlet when the electric motor positions the output member in the first valve-seating position.
Additional features and advantages of the apparatus will become apparent to those skilled in the art upon consideration of the following detailed description exemplifying the best mode of the disclosure as presently perceived.